1. Field of the Invention
The present invention relates to ladders and climbing devices. More particularly, the invention comprises a climbing and descending device having a single central mast and two steps which slide upwardly and downwardly along the mast. Each step has a one-way clutch preventing sliding, so that the two steps may be alternately moved upwardly in a ratcheting scheme. The clutch can be released for enabling the steps to descend. The steps are tethered so that descent during one motion of each step is limited.
2. Description of the Prior Art
Alternatives for conventional ladders having right and left lateral rails and spaced apart rungs spanning the rails are known in the prior art. Included among these alternative ladders are those having a single central vertical pole and associated foot supports. These alternative ladders may serve a specific application or may be intended as more compact general purpose ladders. Among the principal applications of alternative ladders are their adaptability to irregular objects and terrain. For example, monopole ladders for climbing trees and geographic formations have been proposed in the prior art.
U.S. Pat. No. 4,301,891, issued to Jivan Harbian on Nov. 24, 1981, describes a monopole climbing device wherein elements for supporting hands and feet are clutched to the pole. However, foot support elements and hand support elements are provided in unitary paired assemblies causing both feet to be supported at a common elevation along the pole. Similarly, both hands are supported at a second common elevation along the pole. No hand or foot support element is tethered to a second similar element in the manner of the present invention. Further, Harbian causes individual hand and foot support elements to encircle the pole in a non-rotatable manner, vertical sliding being opposed by a separate lever actuated brake. In the present invention, a single common spring biased mechanism prevents both vertical movement relative to the pole and also binds the foot support element to the pole.
U.S. Pat. No. 4,310,070, issued to Spirodon Mastrogiannis on Jan. 12, 1982, describes a monopole climbing device having separate foot supporting elements. Pivoting of each foot supporting element clutches the foot supporting element to the pole by frictionally engaging a guide cable extending along the pole. However, the clutching arrangement of Mastrogiannis is different from that of the present invention, and Mastrogiannis also lacks tethers tethering two foot supporting elements to one another for limiting separation or displacement between the two.
U.S. Pat. No. 3,403,750, issued to Jean Pomagalski on Oct. 1, 1968, describes a monopole lift essentially employing a cable and pulley supported seat. Although this device has a footrest, the two feet are supported by a unitary member. By contrast, the present invention has two independent foot supports which move alternately up and down the pole, the foot supports being tethered to limit separation or displacement from one another. Pomagalski's device lacks the one way clutch enabling ratcheting ascent of the present invention.
U.S. Pat. No. 4,892,170, issued to William P. O'Donnell on Jan. 9, 1990, describes a portable monopole ladder having rungs extending laterally from a central pole. The rungs are employed in generally conventional fashion, there being no foot supports axially slidable along the central pole, nor tethers for tethering foot supports to one another.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.